Silo discharge control

ABSTRACT

This specification discloses a silo suitable for granulated or powder form materials. The silo of the invention comprises a fixed shaft, at least one transfer assembly situated below said shaft and an extractor disposed beneath said transfer assembly. The silo shaft has a convergent hopper in its lower portion and there is an outlet opening in the hopper which provides for free flow of material. At least one decompression hopper is situated in the transfer assembly and is elastically suspended so as to be displaceable in all directions relative to the silo shaft and the extractor. In this way, products leaving the silo form a constantly renewed slope at the rear end of the active part of said extractor.

Emited States Patent 1 Petit I54] SILO DISCHARGE CONTROL Georges Petit,l0, Salonique, Paris, France 221 Filed: Nov. 19, 1971 21 Appl.No.:200,634

[76] Inventor: avenue de Related U.S. Application Data [63] Continuationof Ser. No. 842,545, July 17, 1969,

abandoned.

[30] Foreign Application Priority Data July 24, 1968 France ..68160406[52] U.S. Cl. ..222/56, 222/198, 222/200,

' 222/227 [51] Int. Cl ..B65g 67/56 [58] Field of Search .....2l4/17, 17D; 193/2; 198/59, 198/60; 222/161, 198, 200, 202, 203, 415, 564, 56, 227

[56] References Cited UNITED STATES PATENTS Dickerson ..222/415 51 Mar.27, 1973 Cooper ..222/564 X Dumbaugh et a1. ..222/161 FOREIGN PATENTS ORAPPLICATIONS 1,368,711 6/1964 France ..222/415 Primary Examiner-RobertG. Sheridan Attorney-Breitenfeld & Levine [57] ABSTRACT Thisspecification discloses a silo suitable for granulated or powder formmaterials. The silo of the inven tion comprises a fixed shaft, at leastone transfer assembly situated below said shaft and an extractordisposed beneath said transfer assembly. The silo shaft has a convergenthopper in its lower portion and there is an outlet opening in the hopperwhich provides for free flow of material.

At least one decompression hopper is situated in the transfer assemblyand is elastically suspended so as to be displaceable in all directionsrelative to the silo shaft and the extractor. In this way, productsleaving the silo form a constantly renewed slope at the rear end of theactive part of said extractor.

9 Claims, 33 Drawing Figures PATENTEUmznm $722,747

SHEET 20F 9 IHVENTOR:

reonaes mronueis PATENTEBmzmu SHEET 5 OF 9 INUENTO'R: G'Eouets PETLTRNPIS PATENTEUHARZYIHB 3,722,747

SHEET 8 OF 9 INVFNTOR: QEORGFS PET onucis PATENTEDHARZYISB 3122,74?

SHEET 9 OF 9 RTT RN PJ SILO DISCHARGE CONTROL This application is acontinuation of application Ser. No. 842,545, filed July 17, 1969, nowabandoned.

The present invention relates to the extraction system of silos, hoppersand the like.

In his US. Pat. No. 3,593,892, the applicant, after having referred tothe two most usual procedures for avoiding the formation of arches orconsiderable dead stocks in the silos, namely, firstly the particularsof the internal construction of the silo and secondly the use ofvibrations has proposed various improvements, particularly as regardsthe shape, structure and internal geometry of the silos, with the objectof promoting the flow of all of the dead stocks.

In the aforesaid application, the Applicant indicated the essentialprocedures with the object of improving the silos in their upperportion, comprising the body prolonged by at least one hopper, theseelements being fixed (not vibrated). He pointed out that the lower floworifice forming the outlet of this upper part should be at least equalto the section of natural automatic flow.

Throughout the following specification, this orifice or opening, to bechosen in a manner known per se as regards optimum dimensions, will becalled the outlet.

The present invention is concerned with the assembly of the devices tobe interposed between the aforesaid outlet" and the system used forevacuating materials leaving the silo and generally called extractor,with the object of improving the flow and the extraction of all the massin the silo and thus of avoiding the stagnation and the segregation,which are phenomena strictly connected with the quality of the flowwhich is achieved.

This assembly of devices will advantageously operate in connection withthe devices which have formed the subject of the foregoing patentapplication as already referred to and with the complementary devicesdefined by the present patent application and which are to be providedin other zones of the silo, so that their essential and concurrentaction permits the aforesaid objects to be achieved: total flow withoutstagnation and without segregation. Although numerous types of knownextractors can be used, a conveyor belt guided over rollers will be mostfrequently employed, the materials from the silo reaching this belt in apredetermined zone which is called the extraction zone, the movement ofthe belt carrying the materials from the silo ata transfer speed adaptedto the desired outlet flow of the materials.

One of the essential problems of the extraction is due to the fact that,very generally, the outlet" which is necessary is much larger than theextraction zone of the extractor: by way of example, when the "outlet"has a diameter of several meters, it is clearly impossible, orprohibitive on cost grounds, to use in practice a conveyor belt or anyother extractor of also a large width. Consequently, in order to be ableto use extractors of relatively normal dimensions, which areconventional and are not prohibitive as regards cost, it is necessary tointerpose between the outlet" and the extracting belt a transferassembly with a convergent effect, in order to channel the materials ofthe silo towards the extractor, with a flow opening which decreases fromtop to bottom.

The conventional procedure is to use for this purpose a hopper whichconverges downwardly or an assembly of successive hoppers having theoverall effect of convergence. It is quite evident that, in such atransfer assembly, the most marked phenomena of arches and progressiveclogging have a tendency to be produced.

The conventional solutions used for overcoming these phenomena aregenerally based on the use of the vibration of one or more hoppersand/or of one or more intermediate members of the assembly, thevibrations then either being continuous or cyclic according to aprogram, but in every case with a constant vibrator force (although thisis frequently adjustable). Experience shows that these solutions, whichgenerally are not very efficient, are usually dangerous: or themcompress and compact the material, or they are insufficient, or theydamage the silos and hoppers. These bad results are readily understood,since the vibratory force being used is not constantly adapted to thevariations in the flowability of the product in question.

One of the more complicated of the conventional solutions consists, forexample, in making the state of vibration of certain elements dependenton the pressure of the stream of material at the level of the extractor:when a fall in pressure is detected, it is probable that there is aclogging in the transfer system ahead of the extractor and the vibrationis initiated in the penultimate hopper (the last hopper being that whichfeeds the extractor element and usually called the supply chute) inorder to produce a declogging. It is however apparent that this is apalliative rather than a truly efficient remedy: in actual fact, ifthere is any clogging, it is because the geometry of the transferassembly is not adapted at every moment to the characteristics formingthe pourability of the material.

Furthermore, experience shows that the decrease in the pressure detectedat the level of the extractor usually rather indicates a clogging of thelast hopper or chute rather than of the penultimate hopper, particularlyas regards products which are fairly clogging by nature.

The Applicant has found that the clogging effects are formed from thelast lower surface capable of providing a support for a deposit (inprinciple, the last inclined surface or surfaces before the extractorelement), and then are developed by successive deposits in stratifiedlayers and progressively reach the top parts of the silo.

It is thus pointless under such conditions to vibrate the penultimatehopper, because the pressure liberated by the vibration attempts toengulf an excess of material in the hopper of the extractor, when thislatter has precisely just given signs of clogging on starting up thevibration. The result thereof will be an acceleration of the depositsand of the duration thereof inside the last hopper; the residual passagebecomes progressively more closed, causing vibrations of greaterfrequency until there is complete stoppage, which necessitates manualintervention.

On the other hand, the integral automatic procedure cannot be satisfiedby a constant vibratory force when the flowability is a large variable.The vibratory force, if it is well adapted to certain moments, isdecidedly less adapted to others and is the cause of difficulties.

The pourability of a granular or pulverous product depends on numerousfactors among which can be mentioned the grain size, the water contentand, more generally, the more or less homogeneous composition of theproduct. In practice, not only the industrial products stored in silosshow great differences from one another as regards pourability, but thesame product can itself vary considerably in its pouring capacity: forexample, its pouring capacity can vary enormously between summer (dryproduct) and winter (moist product); furthermore, the pourability can beinfluenced by the previous handling operations on the product, which canfor example produce locally compacting effects; finally, the widevariety of industrial products, especially those originating fromextraction from pits or mines, for example clays, limestones, marls,coals and ores, are far from being homogeneous.

On the other hand, the process referred to above (line 23 on page 2) andproviding for vibration of the penultimate hopper (or those in frontthereof) is found in practice to be unsatisfactory, because it produceswithout fail the progressive clogging of the last hopper or chute (whichis generally that of the extractor itself), because of the trulycramming effect which this latter experiences because of the excessdelivery of material liberated by the vibration and by the unclogging ofthe penultimate hopper.

The present invention provides for overcoming the disadvantages brieflyreferred to above in connection with the conventional transferassemblies interposed between the outlet of a silo and its extractor.

According to a first feature, the transfer assembly according to theinvention comprises one or more decompression hoppers suspended in avery flexible and elastic manner and so as to be very mobile, in orderto permit easy displacements both in the vertical direction and in anyhorizontal direction; these possibilities of easy displacements have avery marked auto-destructive effect on chimneys, stagnations and arches.Furthermore, the decompression hoppers according to the inventionadvantageously have particular structural features and alsocomplementary features, these being inter alia the extraction with arear incline and the extraction section of progressive widths or ofparabolic form, which facilitates in conjunction with the otheraforesaid means the complete mobilization of the mass of the storedproduct the whole being associated if necessary with an anti-clogginglining.

According to another feature of the invention, the different hoppers ofthe transfer assembly are capable of being set in vibration inaccordance with specific vibratory procedures, of which one of the maincharacteristics is that they intervene at an appropriate moment withpossibility of adaptation of the vibratory force being used, this beingcontrary to the general nature of the aforementioned processes, whichintervene in a blind and constant manner, either permanently orcyclically.

In contrast to these latter, the vibration procedure proposed here,which shows a certain degree of intelligence permitting it to discernthe best moment and the necessary intensity for the vibration and thegood position for its operation, can thus be qualified as vibrationbrought into use intelligently.

Moreover, these intelligent vibratory procedures can have progressiveeffects and comprise a cyclic declogging program.

It is to be noted that the intelligence vibratory procedures describedabove can be applied to all the other declogging arrangements, such asinflating cushions, fluidification, rotary air jets, etc., in order tomake them more efficient and less troublesome.

According to another feature of the invention, the hopper of thedecompression assembly has associated therewith a compression board inthe form of a cone or pyramid, which is preferably elastically andmovably mounted axially of the hopper; this board is advantageouslyaccessible each time when possible from outside the hopper and isassociated with an independent vibratory system.

According to another feature of the invention, vibrations which areadjustable in amplitude and/or frequency are used, the adjustment beingeffected in accordance with the instantaneous characteristics of theflow in the silo.

According to another feature of the invention, a particular process ofexcess withdrawal with overflow is used for the products which clogtogether and form masses.

By massing products, there are indicated here those which are capable ofsetting if they remain stationary for too long a period.

This phenomenon frequently occurs with hygroscopic products, as forexample the nitrates, chlorides, etc., which are used in the manufactureof chemical fertilizers and which can become solid in a few hours.

According to another feature of the invention, used in the case ofproducts having very variable flowing capacity, the compacting in thetransfer assembly is anticipated by permanently adjusting the flowaperture of the transfer assembly or extraction zone to theinstantaneous flowability of the product which is passing through it,Therefore, it is not the clogging which is acted upon, this only being aconsequence, but it is the actual reason for this phenomena which isaffected, this being the lack of adaptation of the transfer assembly tothe flowing properties of the product.

Consequently, according to the invention, for the products which have avery variable flowability, it is proposed to interpose an intermediatetransfer assembly between the outlet" and the extractor device, ofwhatever type this may be, such as an extractor comprising a belt,blades, plates, chain, of the Redler or other type, or having a singleor multiple screw or a vibrating trough, etc., comprising at least onehopper which converges downwardly and is capable of being set invibration, preferably intelligently, and below this hopper, at least oneopening control section of variable passage and means which adapt theopening of the control section to the instantaneous load of theextractor.

In a first embodiment, the control section is formed by a hoppercomprising a movable inclined face suspended from a horizontal shaft.

In other embodiments, the control section comprises at least onehorizontally displaceable, motor-driven register which forms theadjustable member determining the opening of the control section.

The load of the extractor can be determined in several ways. It ispossible, as known per se, to associate with the extractor a weighingtable which determines the variations in weight of the products on thefeeding zone of the extractor. It is also possible to determine thevariations in the height of the stream of product discharged by theextractor in the vicinity of the feeding zone or the variations of therear incline, to which reference will be made later.

According to another feature of the invention, there is used incombination with the above devices, in the case of large silos havingseveral outlets or a single and very elongated outlet in the directionof extraction, a method of extraction having several sills or shelfswhich are adjustable, even during the extracting operation, andadvantageously using the methods of extraction comprising acomplementary action with rear slope and with a progressive extractionsection.

According to another feature of the invention, all or some of the abovearrangements are used for achieving:

a. The extraction from fine powder silos .without fluidization andwithout air consumption. This is always advantageous, because thecompressed air is always very costly to produce and store (particularlyif much of it is consumed and if it is wanted in a dry and clean state,like instrument air). Furthermore, the use of air is undesirable forcertain products, such as: powdered coal or coke (dangers of explosions)or cement (danger of degradation with formation of pellets,

- because of residual or accidental humidity).

b. Extraction without segregation. It is frequently desired to avoidthis latter, because:

the"fines generally have a different composition from the coarseparticles, this making the measurements incorrect,

the fines" absorb more humidity,

the fines flow less satisfactorily and are the last to flow, thusfacilitating the formation of considerable dead stocks, which quicklybecome very compact and very hard.

The description which is to follow, taken in conjunction with theaccompanying drawings given by way of example, will enable it to bebetter understood how the invention can be carried into effect. In theaccompanying drawings:

FIG. 1 is a diagrammatic view ofa silo equipped with a decompressionhopper according to the invention,

FIG. la is a section along the section line la-la of FIG. 1.

FIG. 2 shows a transfer assembly comprising a plurality of superimposeddecompression hoppers,

FIG. 3 represents diagrammatically a feeler blade,"

FIGS, 4, 5, 6, 7 and 8 represent different embodiments of a system ofimproved sealing joints, so as not to impede the mobility of thedecompression hoppers TD or of the vibrated hoppers TV,

FIGS. 9 and 10 illustrate two methods of bevelling the improved vibratedhoppers TV, so as not to impede the vibration of these latter,

FIGS. 11 and 12 show oneembodiment of a hopper which incorporates adecompression board, which possibly can be vibrated, preferably inintelligent manner,

FIGS. 13 and 14 illustrate two embodiments of the recycling circuit inthe case of the cyclic declogging when it is not possible to stop thesupply means,

FIG. 15 is a diagrammatic section of a bottom of a silo equipped with anintermediate transfer system having an adjustable opening, as proposedaccording to the invention for products having very variable flowproperties,

FIG. 16 is a diagrammatic view from the right of this assembly,

FIG. 17 is a modified embodiment of this same assembly,

FIG. 18 is another embodiment of this assembly, comprising one or twomotor-driven registers,

FIGS. 19 and 20 are views from the right of modifications which differas regards the position of the two auto-adaptation half-registers,

FIG. 21 is a diagrammatic longitudinal section of modifications asregards the position of the auto-adaptation register,

FIG. 22 is a diagrammatic view of a conventional extraction assemblyhaving a plurality of sills, in the case of a silo with a very elongatedoutlet,

FIG. 23 represents diagrammatically a multi-sill extraction assembly inthe case of a silo having a very elongated outlet and equipped accordingto the invention,

FIG. 24 shows diagrammatically a multi-sill extraction assembly for amulti-outlet silo,

FIG.. 25 shows diagrammatically an arrangement at the upper end of asilo ofv small horizontal section, which is necessary to complete theextraction arran-gement provided according to the invention in order toavoid the segregation,

FIG. 26 shows diagrammatically one modified embodiment of the precedingassembly,

FIG. 27 shows another modification of the preceding assembly, butprovided for silos having large horizontal sections,

FIG. 28 represents yet another modification for those cases wheresegregation is to be particularly avoided FIG. 29 shows diagrammaticallya preferred method oflining an inclined wall of the transfer assembly,which is also applicable to all connecting channels between differentmanipulating units, 7

FIGS. 30, 31 and 32 show modified forms of the preceding lining.

FIG. I shows diagrammatically the base of a silo, with which isassociated a transfer assembly comprising a decompression hopper TDdisposed beneath the outlet" of the silo. Such a transfer assemblycomprising a single hopper is to be used when the outlet" S, needed bythe product in question, is not too large relatively to the dimensionsof the effective extraction zone provided by the extractor.

According to one essential feature, the decompression hopper TD issuspended elastically and in a very flexible manner and also so as to bevery mobile from the upper part of the silo, for example, by means ofsuspension rods having rubber shock-absorbing blocks BA; such asuspension permits the displacement of the hopper in both the verticaldirection and in any horizontal direction. Instead of shock-absorbingblocks, it is however possible to use other arrangements, either alongor in association, giving the suspension similar properties andincreasing the mobility in the horizontal direction.

By way of example, it is possible to mention the arrangements which areknown per se, such as devices comprising springs, chains, universaljoints, Cardan joints, movable straps (such as those frequently used inweighing, particularly for weigh-bridges, and thus permitting a veryhigh mobility to be obtained), etc.

In order to produce a decompression effect, and as shown in FIG. 1, thehopper TD comprises an upper opening section which is larger than theoutlet" 3. Between the extracting band or belt B and the lower part ofthe decompression hopper, no structural or connecting element preventsthe free flow of the products reaching the belt B or the free movementof the hopper (horizontally or vertically). This freedom of movement,which must only be impeded to the least possible degree by anythingother than the produce itself, necessitates the provision on theconventional sealing joints of the improvements which are hereinafterdescribed, in order to control the mobility of the assembly (with anautomatic effect in destroying the clogging) and also in order not toreduce the strength of the vibratory force. This is true for all thedecompression hoppers, which have always required a more or lesscomplete sealing effect.

The conventional sealing system is shown in FIG. 4. The rubber joint Awhich is held in position by rings B, occupies the position in brokenlines Al when it is placed in position. The swelling of the joint isamplified by the vertical movement of the hopper, due to the flexion ofthe shock-absorbing blocks (or of the springs).

As soon as being set in operation, there is deposited in the zone C aquantity of material (raised product or dust deposits which cannot beprevented by the deflecting wall D sometimes provided) which, under theaction of the vibration, is compacted, hardened and causes the joint toswell, this eventually resulting in the perforation thereof. For thesereasons, it is necessary to provide relatively thick joints which aredetrimental to the mobility. In order toovercome these disadvantages, itis proposed to provide the arrangements described in respect of FIGS. 5,6, 7 and 8. L

The arrangement shown in FIG. provides a lower flap E, which is eitherdepending or stuck at E the said flap being made of a rubber having alow coefficient of friction, which will hereinafter be referred to. Thezone C is thus protected and the suspended hopper maintains itsmobility. In order to avoid the joint from slipping under the action ofthe vibrations, there are provided the hoop or band B, the two straps Fand the circular projection G, which can be formed either by asemispherical element which is welded or screwed in position, or by anyother means.

FIG. 6 provides a single rubber joint A, which is preferably of theslipping type, which is stuck at its lower end to the interior of thehopper at E and which is fixed to the upper part by a band B. In orderto facilitate the positioning operation, the joint can be folded alongthe path Al.

FIGS. 7 and 8 comprise the same arrangements, but with the formation ofa decompression D1, which in addition to being useful for the flow, hasthe additional interest of protecting the joints from abrasion due tothe flow of material, without being caused to provide a deflecting wall,such as D in FIG. 4, which has the dis-.

advantage of reducing the flow outlet and of being the point offormation of a clogging, such as H (shown in FIG. 4).

In the case of hoppers having the form ofa truncated pyramid, thedifferent faces of the hopper are given values which are generallybetween 50 and 65. The

slopes preferably vary from one face to the other, in order to establishlack of symmetry in the distribution of the forces which, in conjunctionwith the high flexibility and mobility and with the progressiveextraction, and the slope AR, produce an automatic effect in removingthe deposits of dead stocks as they are being formed (a.s.m. FIG. 1);preferably, and always in the case of a decompression hopper oftruncated pyramid form, the smallest slope is provided on the preferredextraction side which is characteristic of the extractor underconsideration.

Furthermore, according to the invention, there is provided between thedecompression hopper TD and the belt B a space which is sufficient topermit the formation, at the time of extraction, ofa rear slope" tarear" having to be understood relatively to the direction of extraction;see FIG. 1). Numerous tests have shown that the presence of a rear slopewas advantageous, in that it facilitates the flow by increasing theactual length of the extraction zone of the belt, in that the loading ofthe belt is effected outside the zone under pressure situatedperpendicularly of the lower opening of the hopper, and in that theproduct flowing from the silo is set in movement on the belt outside thesaid pressure zone and thus without appreciable slipping and thereforewith an abrasion effect reduced to the minimum.

The hopper TD is advantageously provided with an extraction section EPof progressive width, that is to say, a hopper which increases in sizein the direction in which extraction takes place. This progressiveextraction, of which the form can be either trapezoidal or triangular,or more or less parabolic, or in accordance with any other progressivecurve, etc., is known per se, but its use concurrently with thearrangements already mentioned assists the complete mobilization of themass of stored products.

The centering chute JG for the product on the extractor element B willlikewise be provided with a progressive clearance JP, which increases inthe extraction direction (see FIG. 1).

In this way, there will be obtained a complementary effect as regardsprogression of extraction, a progression of the lateral sloping of theproduct and a decrease in the wear of the extractor element, and moreespecially of the rubber belts.

FIG. 1 represents an advantageous arrangement, which is hereinafterdescribed. On account of the rearward slope ta, the centering member JGof the product on the extractor element is reduced to two guide checksJG, which can be slightly inclined or preferably vertical, or even witha slight reverse slope for the products with a very great tendency toclogging.

The rear slope permits the omission of the last inclined wall whichnecessarily exists at the rear on the conventional chutes, and which isalways the point where clogging originates.

The guide checks JG can be fixed to the lower part of the hopper TD.

This arrangement and that previously described are particularlyadvantageous in the case where the hoppers TD are vibrated, as willhereinafter be explained, because there is no longer an inclined chutewall which is capable of promoting the initiation and the starting of aclogging, and the guide checks will, if necessary, be

freed when the hopper TD, with which they are integral, is caused tovibrate. It should be emphasized here, for justifying the importance ofthe assembly of the proposed arrangements, that the clogging produced insilos and the formation of dead stocks always have their point ofinitiation on the lower edge of the inclined walls (and even sometimesof the vertical walls having a rough or rusty portion or only a slightprojection or irregularity) bordering the lowest outlet openmg.

In any case, it is essential, as soon as products of a somewhat cloggingnature are dealt with, to provide the vibration of the last hopper orchute feeding the extractor element, because if only the penultimate oneis vibrated, there is unavoidably established a start of clogging (ordeposition of dead stock a.s.m.), which is progressively hardened andreaches the upper zones. FIGS. 1 and 2 give an idea of the method bywhich this clogging is progressively formed.

Finally, the decompression hoppers according to the invention arepreferably provided with a lining, which is preferably slippery andelastically deformable for reducing the clogging and which willhereinafter be referred to.

In the case where the opening S or outlet has a too large dimensionrelatively to the extraction zone for only a single decompression hopperTD to be sufficient, a series of decompression hoppers TD TD TD areused, as shown in FIG. 2, each hopper having a suspension system of theaforementioned type, the suspension system of an intermediate hopperpreferably being connected to fixed points independent of the hopperimmediately above: in this way, independently suspended hoppers areobtained, so as not to provide any danger of causing harmful settlingand it is necessary to use suspensions which are very elastic and have avery strong damping action.

All the foregoing, concerned with decompression hoppers, is particularlyrecommended for products having a pouring capacity which is relativelybad but is also relatively constant.

The proposed solutions are found to be insufficient when the product hasa very bad pourability, although fairly constant. In this case, the useof decompression hoppers is generally insufficient to avoid the cloggingeffects. According to the invention, use is then made of vibration. Inthe case of a single outlet, a decompression hopper of the aforesaidtype is used, with which a vibration is associated.

According to the invention, the initiation of a vibration, itsamplitude, frequency and duration, are carefully matched to theinstantaneous state of flow of the products of the silo and its hopper.

The detection of the instantaneous state of flow can be effected invarious ways, particularly by measuring a height or a slope of theproduct at a given level in the silo or the extractor, or by measuringthe deformation of the suspension of one or several hoppers, or bymeasuring the load of the extractor in a certain zone, or by partial ortotal weighing of the extractor.

For measuring the height of the stream at any point, it is advantageousto use a feeler blade of thetype shown in FIG. 3. It must be understoodthat FIG. 3 is only given as an example of a very simple embodiment. Thefeeler blade 12 shown in this figure is adapted to control the height ofa stream v. The blade 12 comprises a curved detecting element whichrests on the stream, the blade itself being suspended by a bracket 1212on a fixed knife edge 13.

By means means of the stop 14a of an arm 14, the pivoting of the blade12 about the knife edge 13, caused by a sudden fall in the height of thestrea m v, causes the operation of a detector I5; this detector is forexample a microcontact, a proximity contact, a mercury tube, a magneticmercury switch, etc.

Depending on the type of microcontact being used, the stop can bereplaced, as is usual, by a camforming sector which has a progressiveaction and does not provide any danger of the contact being damaged.

With materials which have a very strong clogging action, the curveportion 12a is advantageously lined with one of the slippery materialswhich will be hereinafter discussed, otherwise the blade will be quicklysoiled to an extent that frequent cleaning operations become necessary.

According to the invention, the feeler blades are used for controllingthe height of the product downstream (height of extracted stream) andupstream (rear slope) of the extraction. In this sense, the feeler bladeon the rear slope is more advantageous, because it gives an earlierwarning, and avoids having a deficiency on the extractor element.

FIG. 2 shows a feeler blade PP for controlling the height of the streamor flow downstream of the extraction. This figure also shows vibratorsV1, V2, V3, which are associated with the hoppers TDl, TD2, TD3. Whenseveral successive hoppers are associated in order to form a transferassembly, it is essential, if the vibration is used, for this vibrationto affect at least the lower hopper, which has to replace (or form) thecentering chute (or supply chute) of the product on the extractor, asalready explained above.

On the other hand, it is also essential for the declogging or freeing ofthe hoppers by vibration to commence at the lowest point, otherwise thereleased products of the upper hoppers will become jammed in theresidual passage of that hopper which is situated below.

According to one feature of the invention, the feeler blades of the typereferred to are used so' that they initiate several successivevibrations of progressive efficiency as a function of the fall in theheight of extracted stream: for example, a first vibration becomesoperative for a decrease in the flow height of 10 to 15 percent, asecond for a decrease in flow height of 20 to 30 percent and a third fora decrease greater than 50 percent. The duration of the vibrations isadvantageously proportional to the decrease in the detected flow height,the first vibration lasting, for example 2 to 5 seconds, the second for5 to 10 seconds and the third for I0 to 20 seconds. It is a question intotal of a method of vibration having graduated progressive effects,which is a specific feature of the invention. Such a method of vibrationis used for the products which relatively have little clogging action,for example, small coal.

For detecting the load of the suspended hoppers, it is also possible tomeasure the flexion of the shock-absorbing blocks by means of numerousdevices which are know per se for measuring a displacement.

For measuring the load of the extracting belt in a given zone, it ispossible, for example, in a manner known per se, to arrange a weighingplatform beneath the belt. For the extractors which do not use belts,they can be weighed either completely or with a fixed point, in a mannerknown per se.

According to one feature of the present invention, variable andadjustable vibratory forces are preferably used. It is possible, forexample, to employ electromagnetic vibrators which are capable ofcontrolled variations in frequency and/or amplitude. It is also possibleto use unbalanced vibrators having an adjustable speed and/or aneccentricity of the adjustable unbalancing means; a plurality ofvibrators capable of acting separately or in combination can be used togive different vibratory procedures.

For assisting the flow in the silos and the hoppers, it is usual andadvantageous to round them off or to bevel the angles thereof.

It is also desirable to do the same, inter alia, in respect of thevibrated decompression hoppers, but this is troublesome ifit is obtainedby rolling or by bending.

The welding in the angles of the bevelling plates is a satisfactorysolution from the economic point of view and as regards flow.Nevertheless, it has the disadvantage of causing the hoppers to becometoo rigid, and these are then difficult to vibrate and to strip.

In order to overcome these disadvantages, provision is made inaccordance with one feature of the invention, as shown in FIG. 9, forthe bevelling plates to be welded on their upper portion only over alength corresponding to about a quarter or a fifth of their height.Thus, the part which is made rigid will only be the upper part, andthis, because of being covered with the hopper immediately above it andthe slope, is in practice not in contact with the material. All the freepart, which is the longer part, will be able to vibrate at the same timeas the vibrated hopper and at a suitable rate, which will facilitate thecleaning thereof and that of the hopper.

For avoiding the micro-folds due to the vibration always being effectedalong the line aa passing through the terminal points of the welds andcausing a cracking, such as that which is usual for the metals subjectedto alternate stresses at high frequency, this being all the more thecase when the ends of the weld always show a orator zone with burning ofthe plate which weakens resistance at this position, a progressivelyextending indentation cavity is provided, which moves the fold line tobb, that is to say, into a zone where the metal plate is sound and willbe able satisfactorily to resist the fatigue of the metal.

The bevels will advantageously have a decreasing width (from top tobottom), each time that the slopes of the corresponding faces will berelatively small, as shown in FIG. 10.

FIGS. 11 and 12 illustrate diagrammatically as two perpendicularvertical sections one particularly interesting embodiment of a vibratedhopper TV which is suspended by a flexible suspension by means ofshockabsorbing blocks BA. This hopper is equipped with a vibrator Vcapable of causing vertical or horizontal vibrations, as required bycircumstances. In characteristic manner, the hopper is equipped with anassembly 30 forming a decompression platform and comprising one or twohollow prisms 31 forming transverse cross members, with which isassociated a vibrating roof 32 of conical or pyramidal form, which isresiliently and/or movably mounted relatively to the prismatic element31 by means of shock-absorbing blocks 33 or other devices as alreadydescribed above. If there is only one hollow prism 3i, as in FIGS. 11and 12, the seating of the roof 32 is completed by supports provided onanother cross member reduced to a simple plate 34. A vibrator 3S permitsthe roof 32 to be set in vibration independently, and the slope of saidroof will be accentuated to a greater or lesser degree, depending Y onthe pouring capacity of the product under consideration.

The prism 31 forming a cross member'is preferably of the type describedin the aforementioned US. Pat. No. 3,593,892, as a decompression prism."It is thus fast with the vibrated hopper TV, while being accessible fromoutside through openings 31a. As a result, the vibrator 35 isaccessible, so that it can be regulated according to the characteristicsof the flowing product and its maintenance can be assured, even duringthe operation of the installation.

The single or double cruciform prism 31 and the plate 34, because theyform cross members, are able to impede the sufficient vibration of thehopper TV in certain cases. If necessary, the prism or prisms will thenbe out along the lines xx, and the vibrating roof 32 will rest by meansof the blocks 33 on the truncated prisms which form brackets. The plate36 for access to the vibrator 35 and ensuring the connection between thetruncated prisms will then be floating, that is to say, not rigidlyconnected to the said truncated prisms and if fluid-tightness has to beprovided, rubber joints forming a bellows will be provided.

Another point of this arrangement is to make independent the vibrationsof the hopper itself and of its vibrating roof 32, because the demandsas regards vibrations of these two members can vary independently of oneanother and cannot always be satisfied by the effect of a singlevibrator functioning continuously in a blind manner.

Experience has actually shown that, even for products which flowrelatively well, a single and continuous vibration simultaneouslyactuating the hopper and the decompression roof, which is rigidly fixedto it, is capable of compressing the product above the vibrating roofinto a growing deposit which is capable of completely blocking the flow.The zone situated beneath the roof can also be blocked if the deliveryof the roof is greater at certain moments than that of the lower hopper.It is necessary to allow for general and local variations in theflowability.

As a modification, a vibrating roof such as 32, rather than beingmounted above a decompression prism connected to the hopper, can beassociated and usually suspended from an element of the tubular centralchimney, of the type described in the aforementioned patent application,which then descends into the interior of the transfer system. Theinterest of this latter arrangement is that there is no obstacle capableof interfering with the flow in the confined zone of the circuit.

According to another feature of the invention, in order automatically topromote the complete flow of a silo in the case of products which clogvery readily, a

freeing cyclic vibration method is used, in which the last hopper beforethe extractor is vibrated under certain conditions as hereinafterindicated. The feeding of the silo is stopped periodically (the durationof the cycle being adjustable and regulated according to theagglomerating and massing power of the product at the time in question);the extraction continues until the moment when there is produced a fallin the height of the extracted stream or preferably a fall in the rearslope, which initiates a first vibration (of regulated maximumduration), which breaks up the accumulated masses, because at thismoment they are still fresh and friable, and this is shown by a raisingof the height of the stream or of the slope (or of the weight on theweighing platform), which stops the vibration; the same process isreproduced automatically for the other falls in height of the stream orslope, until the initiation of the vibration is no longer able tocompensate for the lack of product. The silo is then completely empty,and it is at this moment that the empty hopper freeing and breakingvibration becomes operative, this being more efficient than the previousvibrations, just because the hopper is empty. Simultaneously, the supplyto the silo is restarted, with the suitable delay, so that the arrivalof the product at the level of the extractor takes place at a suitablemoment, while being preceded by the freeing and emptying of the transferassembly. In this way, a cyclic clearing or freeing is obtained, whichcauses a good internal cleaning of the silo.

Without these arrangements, there would be progressively produced insidethe vibrated hopper and the lower hopper of the silo, and even in theshaft of the silo, clogging effects which lead to an immobilization of alarge part of the useful capacity. These clogging effects are shown inFIG. 1. The vibration would only have occasion to become operative whenthe residual passage would be insufficient to ensure the necessarysupply to the extractor. At this moment, the quantity of deposits willbe such that a very large and certainly possibly prohibitive vibratoryforce will be required, and it will be necessary to have recourse tomanual intervention, and this is inadmissible from an automatic point ofview.

For making the restarting of the supply automatic, the empty vibratedhopper declogging vibration can be synchronized, for example: I

either by the fact that this empty hopper vibration absorbs an intensitygreater than the preceding vibrations, because of the increase inamplitudes (use of an adjustable intensity relay),

or by the fact that this last vibration lasts throughout the cyclewithout the rear feeler blade reassuming its normal position.

The resupply at the satisfactory moment, in order to avoid a lack ofmaterial on the extractor, can raise problems in installations operatingcontinuously and in respect of which there has never been any interestin creating supplementary discontinuities.

In particular, there is no point in completely stopping the supply meansof the hoppers, because of the repercussions which this causes in theautomatic operation of the installation, in view of the fact that,statistically, the major part of the troubles is produced at the time ofrestarting. It is more advantageous to pass automatically to a minimumsupply rate of flow.

On the other hand, for the silos of which the supply operates by the allor nothing" principle, by means of maximum and minimum level contactsthere are normally only problems when the supply means cannot berestarted under load and the response time for the arrival of theproduct is too long in order to ensure the withdrawal by extraction.

In order to avoid these disadvantages, in accordance with one feature ofthe invention, the cyclic declogging or freeing is completed by theaddition of a buffer hopper T: which stores the supplied quantity duringthe freeing period and then restores it. There is thus provided asubstantially instantaneous possibility of resupply, in order to avoid adeficiency.

FIGS. 13 and 14 illustrate as non-limiting examples the use of thisprocess in the case of:

a single outlet silo, supplied by an adjustable delivery belt, which itis not desired to stop, and in this case, the installation can beconstructed according to FIG. 13, and comprises:

a finer mechanism automatically causing the variation of the supply to arate lower than that of the extraction, this occurring N times every 24hours (it being possible for N to be adjustable from 12 times per 24hours to once for every two or seven days, depending on the pourabilityand the clogging nature of the product, the season, etc.),

the bypass Bp which, because of an automatic control initiated by a lowlevel (or weighing system, etc) of the main silo, permits the deliveryof the silo to pass into the hopper Tt, V the hopper Tt, the capacity ofwhich is calculated so that it is able to store the quantity of materialdelivered by the supply means during the complete cyclic freeingoperation, that is to say, during the time necessary for emptying thevibrated hopper TV and for effecting the breaking-up operation, thislatter operation being moreover only a few seconds (2 to 5 seconds),because at this moment the efficiency of the vibration is at its maximumlevel, since the hopper TV is empty and the deposits are sufficientlyfresh.

the recycling extractor El, which returns the stored material to thesilo through the inlet F,

the feeler blade pp, which controls the rear slope ta of the extractor Eof the silo and which controls the resetting of the silo supply positionof the bypass Bp, and also the starting of the extractor El, as soon asthe freeing operation is completed.

This assembly can operate in the following manner:

As soon as the timer mechanism has automatically caused the decrease insupply for giving it a value lower than the withdrawal flow, the silo,or at least the still active part thereof, starts to be emptied. It isto be noted that the inactive part, that is to say, the dead stock, willbe greater as the freeing operations are closer together and theaccumulations will be easily destroyed if they are recent and stillfriable. If one waits too long, the accumulations will assume the curveshown at C0 in FIG. 13 and there will be the danger of the vibrationbecoming inefficient, because of the duration and extent thereof.

When the low level indicator is reached (level with radius weighingplatform on the conveyor E, etc.), the bypass channels the deliveredquantity on to the buffer hopper Tt and possibly gives the order toreassume the normal delivery if the response time demands this.

When the hopper TV is empty, the feeler blade pp detects thedisappearance of the rear slope and starts up the vibration.

The cleaning and then the clearing is effected as already explained.

Each time a vibration is initiated, the cleared product reforms the rearslope and the blade pp stops the vibration, because the defect hasdisappeared.

When the hopper is empty and the last vibration does not restore theproduct, the timing mechanism which is to limit the duration of thevibration (and which this time has gone up to the end of its cycle),stops the latter and simultaneously causes the, resetting of the bypassBp in the feed silo" position and the emptying of the hopper Tt throughthe opening F by restarting the extractor El Because of the slow speedgenerally adopted for the extractor E and because this type of extractoris first of all emptied through the rear, the arrival of the materialhas sufficient time to complete the stream and to avoid a lack ofmaterial.

The hopper Tt is also provided with a vibrator V2 which is set inoperation by a feeler blade PP (so that the emptying of the hopper It isin fact complete).

The arrangement provided for the hopper Tr and the opening F avoids theuse of a recycling elevator.

As shown in FIG. 14, it is possible to omit the extractor E1 and toreplace it by a pivoted gate Pb or a motordriven gate which closesautomatically as soon as the hopper T! is thought to be empty and clean(control by the end of the vibration which itself is controlled by atimer or by any other conventional control means).

The foregoing assembly of arrangements is suitable for products havingan average pouring capacity (decompression hopper) or verybad pouringcapacity (vibrated hopper), this pourability being however relativelyuniform. The arrangements proposed are insufficient for products with awidely variable pouring capacity, particularly those which result froman extraction from pits or mines and subject to large variations inhumidity rates. 7

Under these latter conditions, the use of declogging or freeingvibrations, when the product leaving the outlet of the silo does nothave a sufficient pouring capacity in the transfer assembly loading itto the extractor, is only a half-measure, since the clogging has atendency to be produced from the interruption of the vibratoryprocedure, unless there is a sufficient and rather unforeseeableimprovement in its pourability.

Under these conditions, in accordance with one essential feature of theinvention, the compacting in the transfer assembly is anticipated bypermanently adjusting the flow opening of the transfer assembly to theinstantaneous pourability.

These arrangements are illustrated by FIGS. 15, 16, 17 and 18.

FIG. 15 shows the bottom or base of a silo S, of which Sr is the naturalautomatic flow outlet as defined above. The assembly according to theinvention is interposed between Ss and an extractor E. This extractor,which can be a measuring arrangement, comprises for example an endlessconveyor belt 1 guided over rollers 2. Below the outlet," the assemblyaccording to the invention comprises a hopper 3 suspended at the bottomof the sil o, for example, by sufficiently flexible shock-absorbingblocks 4, for permitting the vibration of the hopper under the effect ofa vibrator 5, without any danger of the remainder of the installationbeing caused to vibrate (and thus without any danger of causing aheaping and compacting of the product in the upper part of the silo S).Situated beneath the hopper 3 is the control section 6, which comprisesin characteristic manner a movable wall 7 which is capable of turningabout a horizontal shaft 7 a. Arranged perpendicularly of the shaft 7aare two lateral walls 7b which are generally fixed.Por ition facing theadjustable valve arrangement 7 is another fixed wall 7c.

The pivoting of the valve arrangement 7 about the shaft 70 is controlledby a positioning jack 8. The jack 8 is characteristically controlled bythe land operative in the region of the belt 1 which is situated beneaththe control section 6. For this purpose, the belt rests in this zone ona weighing platform T equipped with weighing rollers 2a. The load on theweighing platform can control the movement of a beam acting on the jack8, for example, by an all or nothing system, as shown diagrammaticallyin the figure. Under these conditions, the section offered bythe controlsection 6 automatically regulated as a function of the load on theweighing platform, that is to say, of the instantaneous pourability ofthe product. The flow or passage section is thus constantly adapted, thedangers of clogging are eliminated and it is pointless in most cases tocause intervention of the vibration of the hopper 3. However, if thevalve arrangement 7 is open to its maximum extent, the system alwaysdetects an insufficiency in the load on the weighing platform, and itcan initiate the vibration of the hopper 3. The opening of the register,which is always relatively slow (because of the necessary torque) isable to react too slowly, in the event of a sudden large decrease in thepouring capacity, due for example to the passage of a very wet batch ofmaterial. In this case,

' the flow section which can be used at this instant (or even forseveral instants) will be too small to ensure the delivery. The resultthereof is a decrease in the height of the stream v and the setting upof the vibration by the feeler blade or preferably by the weighingplatform TP. All this represents a safeguard against the suddenvariations in the sense of aggravating the poor pourability.

It is obvious that the automatic adaptation will also react in respectof weight variations being caused ,by variations in static and dynamicpressures, this moreover operating in the same direction, and this isadvantageous for the regulation of the pressure on the extraction zoneand thus'for standardizing the value of the extracted apparent density.

in this way, there is provided a very interesting arrangement formeasurement by weight (or desimeter), in the sense that the weighingarrangement being used is bifunctional:

automatic adaptation, assisting the flow and the extraction,

automatic regulation of the apparent density of the extracted volume,this being effected before the passage of the register calibrating theheight of the stream, and no longer, as with the conventionaldosimeters, after the passage of this register. In actual fact, forthese conventional apparatus, a deviation is found and an attempt ismade subsequently to correct this.

The foregoing description thus provides for two types of regulation byweight of the volumetric extraction, from the point of view ofprecision:

the dosimeter for usual precision", which only comprises thebifunctional weighing arrangement as described above;

the dosimeter for fine precision, comprising two weighing arrangementsoperating in series:

the first arrangement, referred to as bifunctional" and situated beneaththe outlet of the silo is used for the automatic adaptation, which formsan excellent preliminary operation as regards regularization of theextracted apparent density; the second arrangement, disposed after theregister for regulating the height of the stream, as with theconventional dosimeters, and completing the regulating action of theautomatic adaptation for obtaining a finer accuracy as regards themeasurement by weight.

The automatic adaptation system is not only of interest as regardsimproving the poor flow properties and the adjustment of the extractedapparent density, but it also avoids the overloading (or the alwaystroublesome over-dimensioning) of the extractor under the maximumpressure being exerted by the products when they are dry and flowingwell.

It is obvious that, instead of the hopper 3, it is possible to use anassembly of superimposed hoppers, as in FIG. 2.

The lateral faces 7b of the control section, and also the face 7c facingthe valve arrangement 7, can with the advantage be lined with a liningwhich avoids the sticking of the materials, that is to say, a materialwhich at the same time is slippery and is capable of slightdeformations, as will hereinafter be explained.

The walls 7b, 70 can with advantage also be capable of being vibrated ormoved slightly, so that it is possible where necessary to bring theminto a position with a slight opposite slope. This arrangement can be ofvery great interest for extreme cases of bad pouring capacities (forexample, for very clayey and humid marls). It would be impossible toapply this without the automatic adaptation", because when the productsare dry, they would exert a prohibitive pressure capable of causing theextractor to jam or to cause rapid wear on said extractor.

It is expedient to point out that the valve arrangement 7 can occupy aposition such as the position shown in full lines in FIG. 15, in whichit is directed obliquely towards the rear of the extractor, thus formingan opposite slope. With the valve arrangement in this position, the flowopening offered to the materials below thelevel of the shaft 70increases from top to bottom (widening effect). Such an arrangement witha wall having an opposite slope is very favorable for the extraction ofclogging products, because it increases the effective length ofextraction. This arrangement also has anti-wear effects for the belt, inconjunction with the rear slope ta.

FIG. 17 is substantially identical with FIG. and the same referenceshave been adopted here for indicating the unchanged elements. As well asthe valve member 7, the control section 6 is here provided with amotordriven register 9, which is displaceable horizontally along aslideway 9a in order to control the passage of materials immediatelybeneath the hopper 3. The register 9 is particularly useful when theclosing of the valve member 7 is made difficult by the pressure of thestream of flowing materials. In this case, the register 9 is moved inthe closing direction (this being possible, since it has a fairly sharpedge 9b for penetrating into the stream). Once the register is closed,the section 6 can be completely or partially emptied beneath it, thisenabling the valve member to be brought to the required closing positionwithout any prohibitive forces. By desired position, it is necessary tounderstand the position corresponding to the indications given by theweighing detector system. Conventional procedures can be used formemorizing the value of the closing of the valve member indicated by theweighing system.

As a modification, provision can be made for only closing the register 9when the positioning jack 8 requires this, because it meets a resistanceto the too great closure. The increase in resistance can be determinedby conventional means, such as a current relay which releases when thecurrent absorbed by the jack exceeds a certain threshold; increase inthe pressure for the hydraulic or pneumatic positioning jacks,flattening of an elastic system (springs and/or rubber shock-absorbingblocks, etc), giving an electric contact when the flexion exceeds acertain adjustable value, etc.

The concurrent use of a control section with an adjustable openingadapted to the pourability of the product, a safety register andvibrators, which only become operative above the control section whenthe automatic adaptation of the opening to the pourability reaches itslimits enables a true automatic condition of the flow to be obtained.

FIG. 18 represents a modification of the invention, which is similar tothat shown in FIG. 3, except that the valve member 8 is here replaced bya sliding register 7, which is connected as above to a positioning jack(not shown).

Such an arrangement has a certain number of specific advantages: theregister 7' authorizes the formation, when it is wide open, of a rearslope 10b, the advantages of which have already been seen.

When 7 is almost closed, it restricts the passage of the extractedstream or flow (at the same time as it reduces the pressure on thebelt).

The rear slope 10b1, provided beneath the register 7 maintains for thisassembly the advantages of this method of loading the belt, of which thegreat interest is that the bringing of the grains up to speed in contactwith the belt is effected free from the pressure of the silo, since itis achieved at the end of the free slope, both in the case of 10b (largeopening) and the case of 10b1 (half-closed). The grains furthestupstream pass beneath the slope (i.e. 10b or 10b1),.of which theupstream portion is under low pressure, being thus brought up to speedwithout slipping (and therefore without any wear).

Finally, the layer in contact with the belt is compacted under thepressure zone and it then behaves like a new extracting belt, of whichthe level is raised by the thickness of the layer, thus ensuring thatthe belt is protected against abrasion.

It can be considered that, in the formation of the stream of products Vcarried along by the extractor belt l, there is superimposition of aseries of lower streams Vi originating from the collapsing of the slope10, which is constantly destroyed and reformed, and upper streams Vsoriginating from the main flow of the silo. The streams Vi reach thebelt 1 with a low kinetic energy and a low pressure, whereas the streamsVs reach the streams Vi with a much greater kinetic energy. Because ofthis fact, the existence of the slope 10 appreciably reduces the wear onthe extractor belt.

The upper faces of the motor-driven registers, such as 7' and 9 areadvantageously lined with very slippery material, such as those whichwill hereinafter be referred to.

With the system according to FIG. 18, the vibration of the hopper 3 canalso complete the action of the registers. It can be initiated either bythe weighing system, which then becomes bifunctional, or by a system forcontrolling the rear slope or level of the stream V, such as the feelerblades 12 and 13-.

It is preferably initiated when the register 7' is towards the end ofits opening travel and the load of the extractor is still insufficientor tends further to decrease.

With the opening of the register, the natural flow slope passes from 10ato 100. At 10c, the upstream feeler blade 12 detects a deficiency ofmaterial. This detection is effected before the detection by thedownstream" blade 13, of a fall in the height of the stream or flow.This advance with detection is advantageous, because it permits a morerapid and consequently more efficient automatic intervention, especiallywhen there is taken into account the relatively large respite which isalways available, because of the relatively slow speeds adopted for theextractors of products which do not flow well and which are generallyover-dimensioned from the sectional point of 35 Other registerarrangements which also form part of 40 the invention can be adopted:

FIG. 19 represents very diagrammatically as a view from the right thetransfer assembly equipped with two lateral and horizontalhalf-registers 7 FIG. 20 shows very diagrammatically in respect of thesame assembly the possible arrangement of two inclined half-registers,which are descendant (7" in full lines) or ascendant(7" in brokenlines).

FIG. 21 shows very diagrammatically a longitudinal section of the sameassembly, equipped with a single rear register which is inclined (7" infull lines) and, as a modification, the arrangement of a single frontregister which is inclined (7" in broken lines).

The inclined arrangements which are descendant and which can be imposedon the question of size are also of interest for a decrease in thecutting force and for the automatic cleaning of the upper surface of theregister.

On the other hand, the two registers 7 and 9 (FIG. 18) can be displacedsimultaneously, while exerting a complementary action for controllingthe passage of the products in the control section.

According to another feature of the invention, in the case of siloshaving several outlets or a very elongated outlet in the extractiondirection, an extraction procedure having multiple sills is used, whichcan be combined with the foregoing arrangements.

The use of several sills has already been obtained in accordance withFIG. 22, in the case of a single elongated outlet, but it has thedisadvantage of not permitting the access to, the regulation and themaintenance of the sills during the flow procedure.

FlG. 23 represents a solution which overcomes this disadvantage andfurther mobilizes the mass of the silo, because of the decompressionzones zd and the extractions by a rearward slope ta. The openings Rgserving for access to the adjustable sills Sr are formed inside thedecompression prisms Pd.

This entire assembly considerably improves the extraction and thecomplete mobilization of the mass of the stored product.

If the prisms show the danger of becoming clogged for certain products,they will beflexibly'. mounted and provision will be made for them to beintelligently vibrated.

FIG. 24 illustrates these arrangements in the case of a multi-outletsilo.

In the embodiment which is illustrated, the silo comprises, for example,three containers M M M each equipped with a suspended decompressionhopper TD or a vibrated hopper TV, of the types which have just beendescribed.

According to one feature of the invention, the hoppers Tml, Tm2, Tm3discharge the products into a channel defined by the extractor belt Band two lateral walls L, the assembly thus determining a trough section.On the belt B, the height of the streams leaving the different hoppersis determined by the sills 51,52,53, which are adjustable in height,which can be formed by vertically movable registers and which preferablyare so arranged that they form decompression zones zd. The containers MM M succeed one another in this order in the extracting direction andthe sills 51, 52,43 are regulated for successively heights. With thisarrangement, the belt is first of all charged with the stream v leavingM the charging or loading of the belt being effected by rearward slope:the product, having banked up, covers the belt well within the pressurezone of the first container, thus forming a first layer of product,which serves as extractor and protector of the belt against abrasion.The streams offlow vthen passes beneath the following container M andits upper part behaves like an extractor belt, the level of which shouldhave been raised from the height b of the stream v Obviously, the heightof the transfer arrangement associated with the container M isdetermined so as to permit the free flow, with rear slope or banking, ofthe products leaving M and reaching the imaginary belt formed by theupper part of the stream v The same occurs in respect of the productsreaching the level of M It is important to point out that the multi-sillarrangement briefly described above only functions satisfactorily inpractice when using hoppers permitting a rear slope or banking.Experience shows that, without this arrangement, accumulations areformed unavoidably upstream of M and M which lead to overflowing if thetrough is not covered or to dangerous and clogging compressions if thetrough is covered.

It must be emphasized that the multi-sill extractions described aboveare applicable for all the types of extractors already previouslyreferred to (line 16, page 5).

increasing stream

1. A silo for materials in granulated or powdered form, comprising afixed silo body provided in its lower part with converging wallsterminating in an outlet opening, a hopper disposed beneath said outletopening, a conveyor disposed beneath said hopper, said hopper being soarranged with respect to said conveyor that material leaving the hoppernormally forms a constantly renewed rearwardly directed slope on saidconveyor with respect to the direction of movement of the materialthereby, the slope being representative of the material flow conditionthrough said outlet opening, declogging means, and sensing meansresponsive to said slope for controlling said declogging means toprevent an eventual clogging of the material within said silo body.
 2. Asilo according to claim 1, wherein said sensing means include apivotally supported feeler blade adapted to engage said slope so thatthe angular position of said blade depends on the material flowcondition through said outlet opening.
 3. A silo according to claim 1,wherein said declogging means include means resiliently mounting saidhopper with respect to said silo body, and means for vibrating saidhopper when actuated by said sensing means.
 4. A silo according to claim1, wherein said declogging means include at least one intermediatehopper resiliently mounted with respect to said silo body between theoutlet opening thereof and the first mentioned hopper and means forvibrating said intermediate hopper independently of said first hopperwhen actuated by said sensing means.
 5. A silo according to claim 1,wherein said declogging means include a decompression platformresiliently mounted in said hopper and means for vibrating said platformwhen actuated by said sensing means.
 6. A silo according to claim 1,including at least one movable closure member for varying the effectivearea of a control section through which material passes after leavingsaid hopper.
 7. A silo according to claim 6, wherein the pressure of thematerial on the conveyor is representative of the material flowconDition through said outlet opening, and including sensing meansresponsive to said pressure on the conveyor portion beneath said hopperfor controlling said closure member.
 8. A silo according to claim 6,wherein said closure member includes a horizontally displaceableregister.
 9. A silo according to claim 1, characterized in that saidsilo body includes a plurality of outlet openings, a hopper beneath eachof said openings, each hopper being spaced above said conveyor by adistance greater than the distance between said conveyor and the hopperimmediately preceding it with respect to the direction of movement ofmaterial by said conveyor, declogging means for each hopper, sensingmeans responsive to the slope corresponding to the respective hopper,for controlling its respective declogging means, and an adjustable sillfor controlling the height of the material moving along the conveyorfrom each hopper.